1. Field of the Invention
The present invention relates to an inkjet print head, and particularly to an inkjet print head including stacked piezoelectric actuator plates and a plurality of ink channel plates.
2. Description of Related Art
Inkjet printers equipped with inkjet print heads for printing on paper or other recording media are well known in the art.
FIG. 1 shows an inkjet head 145 employed in this type of inkjet printer. The inkjet head 145 includes a piezoelectric actuator plate 150 and a plurality of thin metal plates 160. The piezoelectric actuator plate 150 is formed of a ceramic material. The piezoelectric actuator plate 150 and the metal plates 160 are stacked together and bonded with a thermo-setting adhesive. Ink channels 165 are formed in the metal plates 160 through an etching process.
The piezoelectric actuator plate 150 and metal plates 160 are stacked together with interposing thermo-setting adhesive and bonded together by applying heat and pressure. The metal material in the metal plates 160 generally has a larger linear expansion coefficient than the piezoelectric actuator plate 150. Accordingly, the metal plates 160 expand to a larger degree than the piezoelectric actuator plate 150 due to the heat. When the temperature of the metal plates 160 returns to room temperature after the bonding process, the metal plates 160 contract much more than the piezoelectric actuator plate 150. As a result, the inkjet head 145 can warp into a convex shape swelling toward the piezoelectric actuator plate 150 end, as indicated by the broken line in FIG. 1. This warping can cause damage to the piezoelectric actuator plate 150, which is formed of a ceramic material.
To prevent this, a method is conceivable to construct the metal plates 160 using metal plates (for example, Ni 42%-Fe alloy) having a relatively small linear expansion coefficient. By minimizing the difference between linear expansion coefficients of the piezoelectric actuator plate 150 and the metal plates 160, it is possible to reduce the difference in amount of deformation, or shrinkage, in the piezoelectric actuator plate 150 and the metal plates 160 when the inkjet head 145 cools after the bonding process.
However, the metal plates 160 used in this conceivable method are formed of metal plates having a relatively small linear expansion coefficient that is generally not resistant to the corrosiveness of ink. As a result, the lifespan of the inkjet head 145 is shortened.
On the other hand, metal plates that are superior in resistance to ink corrosion generally have a high linear expansion coefficient. As a result, the inkjet head 145 becomes warped or damaged after bonding, as described above, leading to a low yield in the manufacturing process.
In view of the above-described drawbacks, it is an objective of the present invention to provide an improved inkjet print head, in which channels are formed in ink channel plates that are superior in the resistance of ink corrosion, and which is capable of preventing deformation of these plates after bonding.
In order to attain the above and other objects, the present invention provides an inkjet print head, comprising: a piezoelectric actuator plate for being driven by a drive voltage; first and second ink channel plates, each being formed with a plurality of ink channels for guiding ink, the first and second ink channel plates being stacked one on the other, the first ink channel plate having a linear expansion coefficient greater than linear expansion coefficients of the second ink channel plate and the piezoelectric actuator plate; and a thermo-setting adhesive layer provided, between the piezoelectric actuator and the first ink channel plate, for bonding the piezoelectric actuator plate to the first ink channel plate.
In the inkjet print head described above, the linear expansion coefficient of the material used to form the first ink channel plate is larger than those of the other plates (piezoelectric actuator plate and second ink channel plate). Accordingly, the first ink channel plate interposed between the piezoelectric actuator plate and the second ink channel plate has the largest amount of deformation and shrinkage that occurs when the plates cool after the piezoelectric actuator plate is bonded to the first ink channel plate using a thermo-setting adhesive. While warping forces act on the plates on both sides of the first ink channel plate, these forces act in opposing directions and substantially cancel each other. Hence, it is possible to prevent the inkjet head from becoming extremely warped and damaged, thereby leading to high yields in the manufacturing process.